The present invention relates to a method for the stabilization of a higher unsaturated organic compound having at least one double bond in a molecule such as those compounds used in the control of insect pests by the method of mating disruption as a sex pheromone of the insect or, more particularly, to a method for the stabilization of an ester, alcohol, ketone or hydrocarbon compound having at least 10 carbon atoms and at least one double bond in a molecule.
In relation to the pest control in agriculture by using agricultural chemicals, serious problems are noted in recent years including increased resistance against chemicals acquired by the insect species and the toxicity of the chemicals against the health of the agricultural workers as well as consumers of the agricultural products due to the residual amount of the chemicals in the products. As a countermeasure for these problems, biological methods for insect pest control are now under way of intensive investigations, of which the most promising is the method of mating disruption by utilizing various kinds of chemically synthesized sex pheromone compounds as a secretion of the insect females to attract males. It is very important in this method of pest control to keep a constant rate of release of the sex pheromone compound in the field over a long period of time, for example, by the use of the sustained-release dispensers disclosed in Japanese Patent Publication No. 61-16361. In this regard, difficulties are encountered in the use of the sex pheromone compounds for the insect pests belonging to the order of Lepidoptera which are each a long-chain aliphatic compound having at least 10 carbon atoms and at least one double bond in a molecule. The presence of double bonds in such a compound is responsible for the denaturation of the compound by the reaction of oxidation, isomerization, oligomerization and the like at the double bond when the sex pheromone compound is kept under outdoor conditions.
With an object to solve this problem, a method is proposed for the stabilization of a sex pheromone compound by the admixture thereof with an antioxidant or ultraviolet absorber. For example, it is reported in Journal of Chemical Ecology, volume 14, No. 8, page 1659 (1988) that the stability of a sex pheromone compound can be improved by the addition of an antioxidant such as di-tert-butyl hydroxytoluene or tert-butyl hydroxyanisole in combination with an ultraviolet absorber such as 2-hydroxy-4-methoxy benzo-phenone and the like. Further, Japanese Patent Publication 63-12452 teaches that the stability of a higher unsaturated aliphatic aldehyde compound can be increased by the combined admixture of a benzophenone compound as an ultraviolet absorber with an antioxidant and a tertiary amine compound.
Although it is indeed that combined use of a specific antioxidant and a specific ultraviolet absorber synergistically contributes more to the improvement of the stability of a sex pheromone compound having a double bond in the molecular structure than in the use of either one of them alone, no quite satisfactory stabilizing effect can be obtained with any combinations of heretofore known antioxidants and known ultraviolet absorbers. Accordingly, it is eagerly desired to obtain a high stabilizing effect on various sex pheromone compounds by the combined addition of stabilizing agents.
It is proposed in U.S. Pat. No. 4,568,771 that a higher aliphatic unsaturated aldehyde compound can be stabilized against oxidation by the admixture of a tertiary amine compound, benzophenone compound, salicylate compound, benzotriazole compound or cyanoacrylate compound together with or without further admixture of an antioxidant. When the sex pheromone compound is not an aldehyde but an ester, alcohol, ketone or hydrocarbon compound, no very effective method is known for the stabilization of such a compound.